The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Leica APO-Summicron-SL 50mm F2 ASPH and the Sigma 50mm F1.4 DG HSM A for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Leica APO-Summicron-SL 50mm F2 ASPH is the longer of the two lenses at 102mm. The Sigma 50mm F1.4 DG HSM A with a length of 100mm is 2mm shorter. On the other hand, the Sigma 50mm F1.4 DG HSM A has a larger diameter of 85mm compared to Leica APO-Summicron-SL 50mm F2 ASPH's 73mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Leica APO-Summicron-SL 50mm F2 ASPH weighs 740g, which means it is 75g (9%) lighter than the Sigma 50mm F1.4 DG HSM A which has a weight of 815g.
Below you can find the dimension and weight table of the 'Standard Prime Lenses in Leica L Mount for size comparison purposes.
Standard Prime Lenses in Leica L Mount for Size Comparison
Both Leica APO-Summicron-SL 50mm F2 ASPH and Sigma 50mm F1.4 DG HSM A has the same Leica L lens mount. Some of the latest released cameras that are compatible with the Leica L lenses are Panasonic S5 II, Panasonic S5 II X and Sigma fp L.
Sigma 50mm F1.4 DG HSM A is also available in Canon EF , Sony Alpha, Sigma SA and Nikon F (FX) mounts.